The server committed a protocol violation. Section=ResponseStatusLine in c#

I have spent a whole day trying to resolve this. I have a custom webserver and requests to it from Chrome or POSTman ReST client work fine. As soon a s I use webclient or httpwebrequest in c#, I get : The server committed a protocol violation. Section=ResponseStatusLine when trying to transfer a zip file to the client.

I have tried:

public static bool SetAllowUnsafeHeaderParsing20()
{
    //Get the assembly that contains the internal class
    Assembly aNetAssembly = Assembly.GetAssembly(typeof(System.Net.Configuration.SettingsSection));
    if (aNetAssembly != null)
    {
        //Use the assembly in order to get the internal type for the internal class
        Type aSettingsType = aNetAssembly.GetType("System.Net.Configuration.SettingsSectionInternal");
        if (aSettingsType != null)
        {
            //Use the internal static property to get an instance of the internal settings class.
            //If the static instance isn't created allready the property will create it for us.
            object anInstance = aSettingsType.InvokeMember("Section", BindingFlags.Static | BindingFlags.GetProperty | BindingFlags.NonPublic, null, null, new object[] { });
            if (anInstance != null)
            {
                //Locate the private bool field that tells the framework is unsafe header parsing should be allowed or not
                FieldInfo aUseUnsafeHeaderParsing = aSettingsType.GetField("useUnsafeHeaderParsing", BindingFlags.NonPublic | BindingFlags.Instance);
                if (aUseUnsafeHeaderParsing != null)
                {
                    aUseUnsafeHeaderParsing.SetValue(anInstance, true);
                    return true;
                }
            }
        }
    }
    return false;
}

and

<system.net>
  <settings>
    <httpWebRequest useUnsafeHeaderParsing="true" />
  </settings>
</system.net>

in app.config.

I have also tried keep-alive=false and messed with the headers too/

This is the webrequest, which fails on the client2Downloadfile call:

private void sendManifest()
{

    Uri remoteuri = new Uri(Properties.Settings.Default.masterurl);

    SetAllowUnsafeHeaderParsing20();
    using (WebClient client = new WebClient())
    {
        NameValueCollection reqparm = new NameValueCollection();
        reqparm.Add("application", "TestApp");
        reqparm.Add("manifest", manifest);
        try
        {
            byte[] responsebytes = client.UploadValues(Properties.Settings.Default.masterurl, "POST", reqparm);
            string responsebody = Encoding.UTF8.GetString(responsebytes);
            if (responsebody != "")
            {
                using (WebClient client2 = new WebClient())
                {
                    client2.DownloadFile(Properties.Settings.Default.masterurl + "//" + responsebody + "transfer.zip", "c:\\temp.zip");
                }
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }
}

The webserver response can be seen at :

http://gplus2.net:9532/97e456f0-9b57-4315-b03d-40a67f76d440/transfer.zip

Any assistance is greatly appreciated as I have literally run out of ideas. It is obviously a malformed server header, but I have kept it to a minimum.

I had the same issue and I solved it using the following method. I created a custom web client that overrides the GetWebRequestMethod.

  class CustomWebClient : WebClient
{
    /// <summary>
    /// Returns a <see cref="T:System.Net.WebRequest" /> object for the specified resource.
    /// </summary>
    /// <param name="address">A <see cref="T:System.Uri" /> that identifies the resource to request.</param>
    /// <returns>
    /// A new <see cref="T:System.Net.WebRequest" /> object for the specified resource.
    /// </returns>
    protected override WebRequest GetWebRequest(Uri address)
    {
        WebRequest request = base.GetWebRequest(address);
        if (request is HttpWebRequest)
        {
            (request as HttpWebRequest).KeepAlive = false;
        }
        return request;
    }
}

Then I made the request in the normal way like this

using (CustomWebClient client = new CustomWebClient())
        {
            client.Headers[HttpRequestHeader.Authorization] = "Basic " + base64String;
            responseData = client.DownloadData(baseUri);
        }

I struggled with that issue for a long time, and eventually the problem was a custom header that I added to IIS... I copied the value from somewhere and it contained {cr}:

Open IIS Manager -> go to the web site -> on content view, choose "Response Headers".

check the custom headers on IIS, remove headers if they are not needed, and also see if a header has a malformed value.

来源：https://stackoverflow.com/questions/23747973/the-server-committed-a-protocol-violation-section-responsestatusline-in-c-sharp

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webclient